1. Field of the Invention
This invention concerns improvements in and relating to detection and extraction, particularly, but not exclusively, to the detection and/or extraction of uranium ions from solution.
2. Present State of the Art
Extraction routes for obtaining uranium from dissolved sources of uranium, such as sea water and leaching liquors are desirable to enable uranium to be extracted for subsequent use, for instance in the nuclear fuel cycle.
Similarly detection of the level of uranium ions in water and organic systems is desirable for process control and effluent monitoring.
To work effectively as an extractor and/or detector for uranium the system needs to be highly selective to uranium, unaffected by other components which may be present in the same environment, operate over a wide range of environmental conditions and concentrations, be robust and practical in the chemically complex and corrosive systems frequently encountered and also give accurate, repeatable readings in the case of detectors.
Prior art systems face problems in one or more of these areas and it is a principal aim of the present invention to provide improved detection and/or extraction for systems, including, but not limited to uranium.
According to a first aspect of the present invention we provide a method for producing a system adapted to interact with a dissolved species, the method comprising providing a first component incorporating a complexing functionality, X, and a polymerisable functionality, R, the complexing functionality being capable of forming a complex with the dissolved species, and providing a second component polymerisable with the first component, the method involving contacting the first component with a species with which it complexes and subsequently contacting the complexed first component with the second component and polymerising the two to produce a polymer incorporating the complexing functionality X, the method further comprising the removal of the complexed species from the functionality X.
By providing the complexing functionalities in this way specifically targeted functionalities are provided in a fixed position.
According to a second aspect of the invention we provide a method for producing a system adapted to interact with a dissolved species, the method comprising providing a first component including a complexing functionality, X, and a polymerisable functionality, R, the complexing functionality being capable of forming a complex with the dissolved species, and providing a second component polymerisable with the first component, the method involving contacting the first and second components and polymerising the two to produce a polymer incorporating the complexing functionality X.
Preferably the method includes contacting the first component with a complexable species, equivalent to the dissolved species with which it is intended to interact, prior to contact with the second component.
Other options, possibilities and features for the first and second aspects of the invention include the following details.
Preferably the complexable functionality in the first component comprises an ionizable group, preferably ionising at pH""s down to pH 6, more preferably down to pH 4 and ideally down to pH 2 or even down to 1.5.
Preferably the complexable functionality includes or consists of a carboxylic acid group.
The complexable functionality may be selective from functionalities of formula:
xe2x95x90CTCOOH, where T is hydrogen or any halogen, (most preferably chlorine) methyl and halogen substituted forms thereof; or
xe2x89xa1CCOOH; or
PhCOOH.
Preferably the polymerisable functionality of the first component comprises a double or triple carbon bond.
Preferably the polymerisable functionality is of formula: 
XCxe2x89xa1CY
where W, X, Y or Z are, independently, selected from hydrogen, halogens, methyl or halogen substituted methyl groups, nitrogen or carbon based chains. Carbon based chains of 1 to 15 carbon atoms are preferred.
Most preferably the first component is an acrylic acid or methacrylic acid. Chloro-acrylic acid is a particularly preferred first component, with 2-chloro-acrylic acid ideal.
The first component may include a plurality of different molecules. Thus two or more different molecules with complexing and polymerising functionalities.
Preferably the second component includes a polymerisable functionality. The second component preferably includes a double or triple carbon bond.
The polymerisable functionality may be selected from the formula: 
where R1, R2, R3 and R4 are, independently, selected from hydrogen, halogens, methyl or halogen substituted methyl groups, nitrogen or carbon, including carbon based chains.
Preferably carbon based chains of between 1 and 30 carbon atoms are involved.
More particularly the functionality may be of formula: 
where R1, R2, R3 and R4 have the definition provide above and at least one of R5, R6 arexe2x80x94COOHxe2x80x94or halogen substituted forms thereof; or 
where one of R7 or R8 is hydrogen or a halogen and the other is xe2x80x94C6H4R4 or halogen substituted forms thereof.
Preferably two functionalities are provided on the second component. The polymerisable functionalities may be the same or different.
Preferably the second component incorporates one or more amide groups.
Preferably the second component incorporates one or more ester groups. Preferably two amide or ester groups are provided between polymerising functionalities. The second component may incorporate groups according to formula:
xe2x80x94O(CR9R10)xOxe2x80x94where X is between 1 and 8and more preferably 2 to 4 and where R9, R10, are, independently, and independently between X""s hydrogen, halogens, nitrogen or carbon based chains.
Preferably the second component incorporates a glycol, for instance ethylene,propylene, butylene or pentylene glycol.
The second component may incorporate di, tri or higher acrylates or methacrylates.
Preferably the second component is a glycol acrylate or glycol methacrylate and is most preferably ethylene glycol dimethacrylate.
The second component may be provided according to formula: 
The second component may include a plurality of different molecules. Thus two or more different molecules with polymerisation functionalities may be provided.
Preferably the complexed species is a cation, most preferably a metallic ion. The ion may be provided in elemental or molecular form. It is particularly preferred that the complexed species be an actinide incorporating ion, such as a uranium incorporating ion. Most preferably it is the uranyl ion. Preferably the complexed species is provided in substantially pure form. Preferably other potentially complexed species are excluded from the contact method.
Preferably the first component and complexed species are presented to one another in a solvent, for instance water, methanol or di-chloromethane. Preferably the complexed species is added to the first component, most preferably in a gradual manner.
Preferably the first component is provided in a solvent together with a proton acceptor, for instance tri-ethylamine.
Where the complexed species is the uranyl ion, most preferably it is added as uranyl nitrate hexahydrate.
Preferably the mixture liquid is filtered following contact.
The first component and complexed species may be contacted with one another in a ratio varying between 10 to 1 first component to complexed species to 10 to 1 complexed species to first component.
Preferably the first component, whether with or without complexed reagent has the second component added to it.
Preferably the mixture, and particularly the precipitate is filtered and washed.
The ratio of first component to second component is preferably between 1 to 2 and 1 to 50 first component to second component.
Preferably the complexed species is removed from the polymerised product to make the complexing functionality available. Preferably the complexed species is removed by contact with an acid, preferably a concentrated acid, such as nitric acid.
Alternatively or additionally the complexed species may be removed by sonnicating the product. Sonnicating at an energy input of 10 to 1000 watts may be provided with 100 to 300 watts being preferred in this regard. The frequency of sonnication may be between 20 and 200 kHz, more preferably between 50 and 100 OkHz. The duration of sonnication may be between 5 minutes and 5 hours, more preferably 10 minutes to 3 hours and is most preferably between 10 and 20 minutes. Sonnication for up to 200 minutes, more preferably up to 100 minutes and even only up to 30 minutes may be used.
Preferably the polymer is washed with a solvent, such as water, following removal of the complexing species. The washing may be performed as part of a filtration step or subsequent thereto.
Preferably the method includes fixing the polymer is fixed to a substrate. Fixation may be provided prior to or subsequent to complexing species removal.
Fixing may be provided prior to polymerisation, but it is preferred that fixing occur subsequent to the polymerisation process.
The substrate may comprise silica, titania, semi-conductor, for instance germanium, polymeric or metal, for instance gold or platinum.
The first and/or second component may be anchored directly to the substrate. The first and/or second component may be anchored indirectly to the substrate, for instance via an intermediate compound which anchors to the substrate.
Where direct anchoring is provided,preferably the first and/or second component is provided with a surface interacting functionality. For metal surfaces such as platinum and gold, a thiol functionality may be provided. For titania or silica substrates, a silane functionality, for instance a chlorosilane such as trichlorosilane, may be provided.
Where indirect fixing is provided preferably an intermediate compound with a surface interacting functionality and a functionality interacting with the first and/or second component is provided. For metal substrates, such as gold or platinum,preferably a thiol functionality is provided on the intermediate compound. For silicon or titania substrates, preferably a silane functionality, such as chlorosilane is provided on the intermediate compound.
Preferably the functionality on the intermediate compound for interacting with the first and/or second component is a vinyl functionality.
According to a third aspect of the invention we provide a method of retaining a species dissolved in a sample comprising contacting the sample with a retaining system, the retaining system comprising a polymeric material incorporating one or more complexing sites for the dissolved species, wherein the sites are formed by one or more complexing functionalities, the functionalities position being fixed in the polymeric material.
Preferably the dissolved species is a cation, most preferably a metal ion. The ion may be in elemental or molecular form. It is preferred that the dissolved species be a uranium incorporating ion, most preferably the uranyl ion.
Preferably the dissolved species is retained preferentially. Preferably the dissolved species is retained selectively with regard to other species which may be present. Preferably the ratio of the species being retained to retention of other species is greater than 2:1, more preferably greater than 5:1 and ideally greater than 10:1 or even 20:1.
The sample may be an aqueous or organic sample. The sample may be a process stream, waste stream, location in the environment or analytical sample.
The sample may be contacted with the retaining system by flow of the sample over the retaining system, by introducing the retaining system to the sample or by introducing the sample to the retaining system.
Preferably the retaining system is formed by copolymerisation of a first and second component. The polymeric material may comprise the polymerised residues of a first component and a second component. The polymeric material may incorporate the residues of first components having or incorporating formulae: 
XCxe2x89xa1CY
where W, X, Y or Z are, independently, selected from hydrogen, halogens, methyl or halogen substituted forms thereof, or carbon, including carbon based chains. Carbon based chains are 1 to 5, carbon atoms are preferred.
Preferably the polymeric material includes the post polymerisation residues of an acrylic acid or methacrylic acid, for instance, chloro-acrylic acid.
Preferably the polymeric material includes the post polymerisation residues of first components having or incorporating formulae: 
R1Cxe2x89xa1CR2 
where R1, R2, R3 and R4 are, independently, selected from hydrogen, halogens, methyl and halogen substituted forms thereof, nitrogen or carbon, including carbon based chains.
Preferably carbon based chains are between 1 and 30 carbon atoms are involved.
Preferably the residue of this second component incorporates one or more ester groups. Preferably two ester groups are provided between polymerisation sites. The residue of the second component may incorporate groups according to formula:
xe2x80x94O(CR9R10)xOxe2x80x94
where X is between 1 and 8, and more preferably between 2 and 4, and where R9, R10 are, independently, and independently between x""s hydrogen, halogens, methyl and halogen substituted forms thereof, nitrogen or carbon based chains.
Preferably the polymeric material is formed from a co-polymerisation of a first monomer incorporating one or more complexing sites and a second monomer which cross-links during polymerisation with the first.
Preferably the polymeric material incorporates post polymerisation residues of glycol and/or acrylates and/or methacrylates,particularly glycol acrylates or glycol methacrylates and most preferably ethylene di-methacrylate.
Preferably the completing functionalities providing the complexing sites comprise an ionizable group. Preferably the group ionises at pH""s down to 6, more preferably down to 4 and ideally down to 2 or even 1.5.
It is preferred that the complexible functionality be or include a carboxylic acid group. The functionality may be of formula:
xe2x95x90CTCOOH, where T is hydrogen, and halogen, methyl and halogen substituted forms thereof; or
xe2x89xa1CCOOH; or
xe2x80x94PhCOOH.
Most preferably T is chlorine.
Preferably the polymeric material is fixed to a substrate. The substrate may be of silica, titania, semi-conductor, such as germanium,polymeric material or metal, for instance gold or platinum.
Preferably the polymeric material is anchored to the substrate by the first and/or second component residues and/or by intermediate components.
Preferably thiol based attachment is used for metal surfaces, such as platinum and gold. Preferably silane, chlorosilane and ideally tri-chlorosilane based fixing is provided for titania or silica substrates.
Indirect fixing through an intermediate compound residue comprising the residues of a vinyl thiol or vinyl silane may be provided.
The method of retaining the dissolved species may comprise an extraction method. Preferably the extraction method further provides for separating the retaining system and sample following retention of dissolved species. The removal may involve the flow of the sample away from the retaining system and/or the removal of the retaining system from the sample.
Preferably the extraction method further provides for the removal of the complex species from the retaining species. Preferably the dissolved species are more concentrated in the released form than in the feed sample.
The dissolved species may be removed from the retaining system by acid stripping and/or sonnication. Preferably a pH of less than 2, more preferably less than 1.5 and even less than 1 may be employed to remove the retained species from the retaining system.
The method may further provide contacting the retaining system, stripped of retained species with a further sample containing dissolved species.
In an alternative or additional form the method of retaining may include a detection method. Alternatively or additionally the production of an interacting system, according to the first or second aspects of the invention, may include the step of providing the system a detector or detection method. Preferably the detection method further provides for the interaction of the dissolved species, upon retention, with a transducer provided in the system, the transducer providing an output indicative of the dissolved species being retained. The output may be qualitative or quantitative.
The detection method may involve the provision of the polymeric material on the surface of a transducer.
The transducer may provide a chemical and/or optical and/or electrical and/or acoustic and/or radiological output.
The transducer may comprise means for detecting variations in the weight of the polymeric material on the substrate, for instance through the piezo electric effect. A quartz crystal substrate provided on electrodes and with an applied oscillating electric field may be provided. Preferably the frequency of a propagating acoustic wave, perpendicular to the crystal surface, is measured.
Transducer means may be provided comprising a crystal or other form of optical waveguide to which an infrared beam of incident light is applied, below the critical angle. The transducer may monitor attenuation of an evanescent field on the surface of the crystal and/or variation in the spectrum of light leaving the crystal. Attenuated total reflection spectroscopy may be employed in the transducer.
The transducer may provide a quartz crystal micro balance provided with the polymeric material on its surface, the crystal being excited by a beam of radiation with acoustic signals being monitored. The transducer may employ photo-acoustic spectroscopy.
The transducer may comprise a scintillator. The transducer may employ florescence and/or luminescence detection. The transducer may employ an electrochemical detection. The transducer may provide a surface plasma resonance based detection. The transducer may employ an impedance and/or frequency based detection.
According to a fourth aspect of the invention we provide a species retaining system comprising a polymeric material incorporating one or more complexing sites for the dissolved species, wherein the sites are formed by one or more complexing functionalities, the functionalities position being fixed in the polymeric material, a sample containing a dissolved species being contacted with the system in use.
The system may include any of the features, options, possibilities or uses set out elsewhere in this application, including means suitable for their implementation.